**4.3 Two-phase Olive Mill Solid Waste (OMSW)**

The OMSW used for the experiments was collected from a two-phase technology mill. The OMSW was derived from olives with a high ripening index (6.5) and an intense purple colour. Before use the small stone pieces were removed by sieving the OMSW through a 3.15 and 2.00 mm sieve. Two influent substrate concentrations were used for the experiments: 35 g COD/L (OMSW 1) and 150 g COD/L (OMSW 2). These concentrations were obtained by dilution of the collected waste. The features and composition of these twophase OMSWs are summarised in Table 1.


COD: total chemical oxygen demand; SCOD: soluble chemical oxygen demand; TVFA: total volatile fatty acids (as acetic acid); Alkalinity (as CaCO3). Values are averages of five determinations; there was virtually no variation (less than 3 %) between analyses.

Table 1. Composition and features of the OMSWs.
